To meet the demand for wireless data traffic, which has increased since deployment of 4th-generation (4G) communication systems, efforts have been made to develop an improved 5th-generation (5G) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘beyond 4G network’ or a ‘post long-term evolution (LTE) system’.
It is considered that the 5G communication system will be implemented in millimeter wave (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To reduce propagation loss of radio waves and increase a transmission distance, a beam forming technique, a massive multiple-input multiple-output (MIMO) technique, a full dimensional MIMO (FD-MIMO) technique, an array antenna technique, an analog beam forming technique, and a large scale antenna technique are discussed in 5G communication systems.
In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud radio access networks (RANs), ultra-dense networks, a device-to-device (D2D) communication, a wireless backhaul, a moving network, a cooperative communication, coordinated multi-points (CoMP), reception-end interference cancellation, and the like.
In the 5G system, a hybrid frequency shift keying (FSK) and quadrature amplitude modulation (QAM) modulation (FQAM) and a sliding window superposition coding (SWSC) as an advanced coding modulation (ACM) scheme, and a filter bank multi carrier (FBMC) scheme, a non-orthogonal multiple Access (NOMA) scheme, and a sparse code multiple access (SCMA) scheme as an advanced access technology have been developed.
A wireless communication system has been progressed to support a higher data rate to satisfy a continuously increased demand for wireless data traffic. For example, a wireless communication system has been progressed to improve a frequency efficiency (spectral efficiency) based on communication schemes such as an orthogonal frequency division multiple access (OFDMA) scheme, a MIMO scheme, and/or the like in order to increase a data rate.
In particular, a demand for data traffic has been accelerated according to an increase of a demand for a smart phone and a tablet PC and an explosive increase of applications which require large amounts of traffic according to this. So, it is difficult to satisfy a demand for wireless data traffic which is rapidly increased only by communication schemes for improving a frequency efficiency.
So, there is a growing interest in a wireless communication system which uses a super high frequency band to solve an explosive increase in this demand for wireless data traffic. However, in a case of communicating using the super high frequency band, a propagation loss such as a path loss, a reflection loss, and/or the like is increased due to a frequency characteristic of the super high frequency band, and a service coverage may be decreased since a range of a propagation shortens. So, the wireless communication system which uses the super high frequency band may expand a service coverage by mitigating a propagation loss of a propagation using a beam forming scheme to increase a range of a propagation.
Meanwhile, for supporting the beam forming scheme, there are a digital beam forming scheme through a plurality of radio frequency (RF) paths using a MIMO processing in a digital domain and a pre-coder or codebook (or will be referred to as a transmit pre-inverse fast Fourier transform (Tx pre-IFFT)/receive post-fast Fourier transform (Rx post-FFT) scheme) and an analog beam forming scheme using a plurality of analog/RF elements (e.g., a phase shifter, a power amplifier (PA), a variable gain amplifier (VGA), and an antenna structure) (or will be referred to as a Tx post-IFFT beam forming/Rx pre-FFT beam forming scheme).
In the digital beam forming scheme, for increasing a beam forming gain, an expensive digital to analog converter (DAC) and analog to digital converter (ADC) may be used and complexity of implementation may be increased.
Further, in the analog beam foil ling scheme, a limitation may occur in an aspect of effectively operating frequency resource or maximizing a beam forming performance when operating beam forming.
So, a hybrid beam forming scheme in which the digital beam forming scheme and the analog beam forming scheme are combined has been proposed for effectively operating a beam.
Meanwhile, a general millimeter wave (mm-wave) cellular system has used the analog beam forming scheme for preventing a phenomenon that a signal to noise ratio (SNR) of a received signal is degraded due to a high path-loss characteristic. In the analog beam forming scheme, a signal transmitting apparatus forms a directional beam pattern, designs an analog beam through a closed-loop beam training process which selects an optimal beam based on feedback information from a signal receiving apparatus, and various analog beam designing schemes have been proposed.
In particular, a standard such as an institute of electrical and electronics engineers (IEEE) 802.11ad standard, an IEEE 802.15.3c standard, and/or the like have proposed a scheme of selecting an analog beam based on a process which sequentially steers a wide beam (or a sector beam) and a narrow beam without channel information.
As described above, the standard such as the IEEE 802.11ad standard, the IEEE 802.15.3c standard, and/or the like selects an optimal beam based on a beam training scheme of a closed-loop scheme including two processes in order to decrease training overhead. That is, the standard such as the IEEE 802.11ad standard, the IEEE 802.15.3c standard, and/or the like selects an optimal beam based on a process which sequentially steers a wide beam and a narrow beam.
In the steering process, a wide sector beam used in a beam training initial process may not normally transfer a training signal in an outdoor environment unlike an indoor environment, so it may be undesirable to apply an analog beam selection scheme proposed in the standard such as the IEEE 802.11ad standard, the IEEE 802.15.3c standard, and/or the like to an mm-wave cellular system.
Further, an object of operating a beam in the standard such as the IEEE 802.11ad standard, the IEEE 802.15.3c standard, and/or the like is to effectively form a beam link focused on selecting an optimal beam. So, the analog beam selection scheme specifies a scheme of designing or selecting only an analog beam without channel information, so the analog beam selection scheme does not guarantee an optimal transmission performance considering an actual channel environment.
Meanwhile, a hybrid MIMO scheme using an analog beam and a digital MIMO scheme has proposed a scheme of selecting an analog beam, estimating an effective channel formed by the selected analog beam, and then designing a digital MIMO scheme.
However, the analog beam selection scheme proposed in the hybrid MIMO scheme selects an analog beam without estimating a channel for each of antennas supported in the hybrid MIMO scheme in order to decrease overhead due to channel estimation, so the analog beam selection scheme proposed in the hybrid MIMO scheme does not guarantee an optimal transmission performance considering an actual channel environment like analog beam selection scheme proposed in the standard such as the IEEE 802.11ad standard, the IEEE 802.15.3c standard, and/or the like.
So, there is a need for a scheme of operating a beam by considering a channel status in a communication system supporting a hybrid MIMO scheme.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.